There are several ways to look for keywords. Some search engines have good own features, free services and professional services. Professional services offen even do offer competitive analysis, where one may see how many pages are competing. Furthermore they give suggestions on local preferences in spelling or special terms. I successfully tried wordtracker: www.wordtracker.com

Furthermore I got a list of free and premium services at:
http://www.folden.info/searchengineoptimization.shtml